Nicotine is one of the most addictive drugs known to man.
I don't know about that because I used to smoke all the time like when partying, but when I didn't want to I went months without smoking and it wasn't hard. Like I stated earlier, I think it has to do with people who become addicted being low in niacin as nicotine is very similar to niacin in the body as well as it's molecular structure. Smoking gives their body what it needs, they are self medicating. Also, it's the ritual of smoking that get a lot of people addicted. The smoke, the heat of the smoke, and holding the cigarette is what they are addicted to not necessarily the nicotine. This reason is why a lot of people get "addicted" to smoking herb. I learned this when I changed from smoking to vaping, and seeing how people reacted.
They are also addicted to the additives in the cigarettes which can contain over 400 additives. I noticed some people who smoked additive free tobacco like American spirit, think it's strong compared to other brands which makes sense because if you open both cigarettes you will see the American spirit is actual tobacco leaf shredded up, while most other brands are flakes, and stem that have been sprayed with nicotine and a whole bunch of nonsense.